Your laptop's power adapter cord converts the 100 to 240 volts of current from your outlet into the much lower voltage necessary to run your portable computer. Although all adapter cords perform this conversion, not all cords will work with your laptop. Laptops offer different connector shapes and sizes and require a specific adapter connector tip to supply the converted electricity to the machine. To use one cord among numerous laptops, you must verify that the wattage provided by the cord, as well as the connector tip are compatible with each laptop.
Every laptop requires a specific number of watts to charge the battery and power the machine. Your laptop's specific watts requirement can be calculated by multiplying the laptop's volts and amps, designated by a "V" and "A" respectively, found in the manual or on the machine's underside. A laptop that requires 16V and 4A, for example, would need an adapter that carries at least 64W. When it comes to wattage, choose an adapter that offers more than you need, never less. An adapter that offers 70W or even 90W would work fine for the example laptop, while an adapter that offers only 60W would be too low.
In addition to wattage, you need to match the adapter's tip to the connector in your laptop. Some laptops require an adapter with a small, round connector, while others need an oval-shaped tip. Still others require a tip that resembles a figure eight. Take care when trying a different cord with your laptop, as what may appear to match may not. Never force the connector into the adapter jack, as you may knock the adapter port loose, which will prevent charging no matter what adapter cord you use.
If you are looking for a replacement or an extra power adapter cord, don't discount third-party brands. These adapters work exactly the same as brand-name cords but are easier on your wallet. Most adapter retailers offer an accessory "lookup" catalog, which shows you a list of compatible adapter cords once you choose your laptop's brand and model number. This helps take the guesswork out of shopping for the proper connector and wattage and allows you to purchase what you need for less than name-brand items cost.
For owners who have multiple laptops that span a few brands and models or who own numerous laptops that require different adapter tips for charging, universal chargers can help ease the hassle of organizing multiple adapter cords. Universal chargers are available with multiple tips, allowing the single adapter to charge multiple laptops so long as the proper tip is attached. When looking for a universal charger, keep the necessary wattage of your laptops in mind and find a charger that provides more than you need to ensure proper charging on all. Not all universal chargers will have tips that cover every single laptop connector shape, so verify that your laptops are compatible with the included connector tips.